from lxml import etree

context = etree.iterparse(r'D:/tmp/latest/zhwiki-latest-pages-articles.xml/zhwiki-latest-pages-articles.xml', events=('end',), tag='page')
for event, elem in context:
    process_page(elem)
    elem.clear()
    while elem.getprevious() is not None:
        del elem.getparent()[0]
        print(elem)
        break;